1. Field of the Invention
The present invention relates in general to means for illuminating the exterior of the eye and its surrounding structure during ophthalmological examination and measurement. Specifically, the present invention is directed towards a means for illuminating a Hertel-type exophthalmometer, as seen in American Journal of Opthalomology, June 1987.
2. Description of the Relevant Art
There are known various means for illumination of the eye in ophthalmological examination. Such light devices, for example, are disclosed in U.S. Pat. Nos. 3,583,795; 3,847,470; 4,265,519; and French patent number 1,583,436.
U.S. Pat. No. 3,583,795 discloses a form of ophthalmoscope having an elongated light-conducting rod. The light from this rod is directed toward and into the patient's eye by means of a mirror. The light-emitting member disclosed is contained within a handheld ophthalmoscope and is used principally for an examination of the interior of the eye, rather than for a light source for examination of the external eye area providing sufficient reflected light to illuminate the measuring scale of an exophthalmometer.
U.S. Pat. No. 3,847,470 discloses an indirect binocular ophthalmoscope having a single prism and lens system connected to an illuminating arrangement contained internally within the ophthalmoscope, and having a motor driven cooling air ventilator located in a single lamp housing. The disclosed device is directed towards illumination of the interior of the eye with a hand held binocular ophthalmoscope, with the light emitting means being contained within the ophthalmoscope. Thus, the disclosed invention is not suitable for attachment to a Hertel-type exophthalmometer without structural modification of the exophthalmometer.
French Patent 1,583,436 discloses an ophthalmoscope having an internally-situated light-emitting means consisting of light-carrying fiber optic material arranged around a contact lens for illuminating and viewing of the interior of the eye. The disclosed ophthalmoscope is therefore not suitable for illuminating the exterior portion of the eye, and would require structural modification of the exophthalmometer in use therewith.
U.S. Pat. No. 4,265,519 discloses a wide angle indirect ophthalmoscope along the lines of the above-mentioned French patent, including optical fibers built into a contact lens for the viewing of the interior of the eye. The disclosed invention is therefore not directed towards producing sufficient illumination for the exterior of the eye area, and is drawn towards the reduction of reflected illuminating light rather than the production of reflected illuminating light off of the eye surface as in the present invention.
Thus, it can be seen that the relevant art is fundamentally different in purpose, structure and function from the presently disclosed invention.
It is customary in an ophthalmological examination to measure the protrusion of the eyeballs, i.e. exophthalmos, from their surrounding sockets, i.e., orbits, by taking a measurement of the distance from the lateral rim of the orbit to the apex of the cornea. After such measurement is taken, the value may be compared between each eye and compared to normal values for indications of pathology.
These measurements are most often taken with a Hertel-type exophthalmometer. The Hertel-type exophthalmometer is a device for measuring the protrusion of both eyes with one examination. The Hertel-type exophthalmometer is placed before the patient's face and a reflected image of the eye from lateral orbital rim to the apex of the cornea is cast upon a forward facing measuring scale enabling the operator to obtain a measurement of this lateral distance from a frontal observation. However, normal room lighting is often insufficient to fully illuminate the patient's eye area and thereby reflectively illuminate the exophthalmometer's measuring skill. This lack of illumination can result in inaccurate measurement of eye protrusion.
In the past, various sources of additional lighting have been used with the exophthalmometer. These past forms of additional lighting have suffered from either a lack of ability to be concentrated on the area under examination, as with increased indirect lighting, or required a use of the operators hand to direct the light source, thus requiring the removal of the operator's hand from the exophthalmometer, leading to unsteady placement of the exophthalmometer.
While many lighting devices are known and used in ophtholmological examination, ranging from complex fiber optic devices to a simple hand held flashlight, none have been adapted to provide a point specific light source to allow the measurer to use both hands when utilizing the Hertel-type, exophthalmometer until the current invention.